Electrode metal material, capacitor and battery formed of the material and method of producing the material and the capacitor and battery

ABSTRACT

The present invention relates to an electrode metal material for batteries, capacitors, etc, used in contact with non-aqueous electrolyte, and particularly to a capacitor formed of the electrode metal material, and provides a valve metal material capable of decreasing the internal resistance of the capacitor. The electrode metal material comprises a valve metal material and numerous carbon particles included in the surface of the valve metal material. The carbon particles are further fixed in the surface of the valve metal material so as to expose to the surface. The electrode metal material is coated with an activated carbon layer and used as a double-layer electrode for an electric double-layer capacitor. The carbon particles included in the surface ensure conduction between the activated carbon layer and the valve metal material. With this configuration, even if the surface of the valve metal material is oxidized, the internal resistance of the electrode is not decreased, the internal resistance of the capacitor is decreased, and the capacitance of the capacitor is increased.

[0001] This is a Continuation-In-Part application of Ser. No. 09/381,680filed on Sep. 23, 1999, now abandoned.

FIELD OF THE INVENTION

[0002] The present invention relates to an electrode metal material forelectrical components such as capacitors and batteries which are used incontact with electrolyte, to a capacitor and a battery formed of theelectrode metal material, and to a method of producing the electrodemetal material and the capacitor and battery thereof.

PRIOR ART

[0003] At present, there are, for example, electric double-layercapacitors and electrolytic capacitors available as electricalcomponents which are used in contact with electrolyte. Such electricdouble-layer capacitors have been applied to large-capacitancecapacitors chargeable at up to about 3 V, and used for backup powersources of microcomputers, memory devices, timers, and the like.

[0004] Typically, an electric double-layer capacitor comprises a pair ofpolarizable electrodes or double-layer electrodes disposed face-to-facevia an insulating separator therebetween and immersed in electrolyte.The electrode is produced by applying an activated carbon layer on thesurface of an electrode metal material made of a valve metal and used asa mechanical supporter and, at the same time, electric collector.

[0005] Some types of electric double-layer capacitors use anorganic-solvent based electrolytic solution as electrolyte, such as atetraethyl ammonium salt which is added to an organic solvent, such aspropylene carbonate. The examples of conventional electric double-layercapacitors using organic-solvent based electrolyte include a type inwhich a pair of electric double-layer electrodes is wound and enclosedin a container, and another type in which a pair of double-layerelectrodes is laminated or stacked, both types having been disclosed inU.S. Pat. No. 5,150,283.

[0006] In the case of the winding type of capacitors, as shown in FIG.7, an electrode metal material 1 is formed of etched aluminum foilhaving a thickness of 20 to 50 μm, and a paste obtained from a powdermixture of activated carbon particles, a desired binder and a desiredconductive agent is applied to the above-mentioned metal foil to form afilm. This film, that is, an activated carbon layer 30 (a polarizableelectrode) mainly consisting of activated carbon particles, is used toform an electric double-layer electrode 3.

[0007] A lead 6 is connected to each of the electrode metal materials 1of the pair of electric double-layer electrodes 3 and 3, respectively.These electrodes 3 and 3 are disposed face-to-face with a separator 5therebetween and wound like a coil. The electric double-layer electrodesis immersed in non-aqueous electrolyte under vacuum to impregnate theactivated carbon layers 30 and the separators 5 with the electrolyte,then placed in an aluminum case 70, the opening 7 of the aluminum case70 being sealed with a watertight packing 8. The electrolyte in theelectric double-layer capacitor has used polypropylene carbonate as anorganic solvent, and a tetraethyl ammonium salt as an electrolyte, forexample.

[0008] Furthermore, in a button-type electric double-layer capacitor,schematically shown in FIGS. 9 and 10, activated carbon layers 30 arejoined to disc-like sheets 1 made of a valve metal material,respectively, to form a pair of double-layer electrodes 3. The pair ofdouble-layer electrodes 3 and 3 are disposed face-to-face via aninsulating separator 5 therebetween, and accommodated in a metalcontainer comprising two mating members. The valve metal material sheetsof the two double-layer electrodes are joined to the inner surface sidesof the bottom member 60 and the lid member 61 of the metal container.Both the bottom and lid members are joined to each other so as to bewatertight by using an insulating ring packing 69 at the peripheralportion thereof. The interior of the capacitor is filled withnon-aqueous electrolyte so that the double-layer electrodes and theactivated carbon layers are immersed therein sufficiently. Thenon-aqueous electrolyte is a solution of tetraethyl ammonium perchlorateadded in propylene carbonate in the same way as described above.

[0009] An electrolytic capacitor is known as a capacitor in whichnon-aqueous electrolyte is used. In the anode of the capacitor, adielectric film is formed by chemically treating the valve metal foil.In the cathode, the valve metal foil is used as it is. Usually, both theelectrodes are disposed face-to-face, wound into a coil, andhermetically enclosed in a container while being immersed inelectrolyte.

[0010] In the case of the conventional electric double-layer capacitor,the valve metal sheet or foil, on which a polarizable electrode isformed as a film, has a naturally oxidized film specific to the valvemetal constituting an electrode structure while the foil is handled.When this foil is used to form an electrode structure, a thin,insulating oxidized film 4 is frequently formed at the interface betweenthe aluminum foil 1 used as a valve metal material and the polarizableelectrode 3, as schematically shown in FIG. 6.

[0011] Furthermore, the above-mentioned non-aqueous electrolytetypically includes slight amounts of water and oxygen. For this reason,the valve metal material constituting the electrode structure reactswith the water content in the electrolyte during use of the capacitor,and the surface of the metal is oxidized. Therefore, when the electricdouble-layer capacitor formed of this kind of metal is used for extendedperiods of time, its equivalent series resistance (ESR), i.e., theinternal resistance of the capacitor used as a power source, increasesgradually, and, in some cases, its capacitance decreases.

[0012] This problem due to the oxidation of the metal portion of theelectrode has also occurred in the case of the button-type electricdouble-layer capacitor in the same way.

[0013] Furthermore, the anode of the electrolytic capacitor usingnon-aqueous electrolyte is provided with a dielectric insulating layerformed by anodizing a valve metal such as aluminum. In addition, itscathode in direct contact with the electrolyte is also formed of thevalve metal such as aluminum. In this case, an oxide film is formed onthe surface of the metal used for the cathode because of oxidation withthe water content in the electrolyte. This causes a problem of thecapacitor increasing in internal resistance, just like the problemdescribed above.

[0014] With respect to batteries using electrodes in contact tonon-aqueous electrolyte, a lithium ion secondary battery is known whichhas high charge-discharge cycle performance with high energy density ina compact shape.

[0015] A lithium ion secondary battery, as shown in FIG. 11, comprises apositive electrode 35, a negative electrode 37, facing to the positiveelectrode, a film separator 5 for separating both electrodes 35 and 37,and a non-aqueous electrolytic solution in which both the electrodes areplaced and contained in a casing 71. The positive electrode 35 is, as anexample, formed of a mixture of positive active substance such asLiCoO₂, conductive material such as acetylene black, and a binderincluding carboxylmethylcellulose and polyflorovinylidene which mixtureis applied on both sides of aluminum foil as an electrode metal material1 for an electric collector. On the other hand, the negative electrode37 is formed of a mixture of negative active substance such as graphiteand a binder such as carboxylmethylcellulose and styrene-butadienerubber which mixture is applied on both sides of copper foil as anelectric collector. The electrolytic solution is a non-aqueous solventof a mixture of propylenecarbonate and 1,2-dimethoxyethane containingLiPF₆ as electrolyte. A porous polypropylene film is used as aseparator.

[0016] In conventional lithium ion secondary batteries, aluminum foil isformed with natural oxide film on its surface during dealing with thefoil so that thin isolating film have often been formed in the interfacebetween the aluminum foil and the positive electrode on the aluminumfoil.

[0017] Further, since the above non-aqueous electrolytic solution alsocontains slight amount of water and oxygen, the aluminum foil in thebattery have been oxidized on its surface, in use, gradually over longtime due to reaction of aluminum surface with water in the electrolyticsolution, causing a lithium ion secondary battery to increase inequivalent series resistance, i.e., internal resistance and resulting inlow capacity at high discharge rate.

SUMMARY OF THE INVENTION

[0018] Accordingly, an object of the present invention is provide avalve metal material capable of being formed into electrodes used incontact with non-aqueous electrolyte to reduce internal resistance of acapacitor or battery.

[0019] Another object of the present invention is to provide a method ofproducing a valve metal material capable of being formed into electrodesused in contact with non-aqueous electrolyte to reduce internalresistance of such a capacitor or battery.

[0020] A still another object of the present invention is to provide acapacitor capable of having a low internal resistance by restricting thechange in the resistance of the electrode metal material constitutingthe electrodes used in contact with non-aqueous electrolyte.

[0021] A still another object of the present invention is to provide anon-aqueous secondary battery having low internal resistance byrestricting the change in the resistance of the electrode metal materialconstituting the electrodes used in contact with non-aqueouselectrolyte.

[0022] A yet still another object of the present invention is to providea method of producing a capacitor capable of having a low internalresistance by restricting the change in the resistance of the electrodemetal material constituting the electrodes used in contact withnon-aqueous electrolyte.

[0023] A yet still another object of the present invention is to providea method of producing a non-aqueous secondary battery having lowinternal resistance by restricting the change in the resistance of theelectrode metal material constituting the electrodes used in contactwith non-aqueous electrolyte.

[0024] An electrode metal material in accordance with the presentinvention is formed of a valve metal material containing carbonparticles on the surface, and is used to form electrodes. The carbonparticles in the carbon-containing metal material ensure direct contactwith a conductor (including electrolyte) to electrically connect theelectrode metal material to the conductor.

[0025] In particular, the carbon-containing metal material comprises avalve metal material and numerous carbon particles fixed in the surfaceof the valve metal material and exposed to the surface. In the presentinvention, the carbon particles may be projected slightly so as to beexposed to the surface of the valve metal material in order to enhancethe conductivity and joining characteristic to a conductor to becomecontact therewith.

[0026] The electrode metal material in accordance with the presentinvention may be used to obtain electrode structures used in contactwith non-aqueous electrolyte. This kind of carbon-containing metalmaterial itself may be an electrode making contact with electrolyte.Alternatively, the electrode metal material may have an activated carbonlayer coated on the surface, i.e., a polarizable electrode. The formercorresponds to the cathode of an electrolytic capacitor, and the lattercorresponds to the double-layer electrode of an electric double-layercapacitor.

[0027] Further, the electrode metal material may be used to support apositive electrode including a positive active substance on the surfaceof the electrode metal material, the positive electrode being used for anon-aqueous electrolytic secondary battery, e.g., a lithium ionsecondary battery.

[0028] In the electrolytic capacitor, the carbon particles of thecarbon-containing metal material, exposed to the surface thereof, canmake direct contact with the electrolyte to ensure conductivity betweenthe metal material and the electrolyte. In addition, inside the electricdouble-layer capacitor, the carbon particles of the carbon-containingmetal material, exposed to the surface thereof, can make direct contactwith the activated carbon layer to ensure conductivity between the metalmaterial and the activated carbon layer. Further, in the lithium ionsecondary battery, the carbon particles of the carbon-containing metalmaterial are exposed to the surface thereof, to make direct contact withthe active substances in the positive electrode, ensuring conductivitybetween the electrode metal material and the positive electrode.

[0029] In any of the cases, even if the carbon-containing metal materialmakes contact with electrolyte solution, and the metallic surfacethereof is oxidized by water contained in non-aqueous electrolyte, theconductivity noted above remains almost unchanged over long timeperiods.

[0030] More particularly, numerous carbon particles may project on thesurface of the valve metal material. Therefore, it is preferable thatonly the metal surface of the valve metal material may be removed suchthat the carbon particles are left projected on the removed surface.This projection configuration of the surface of the valve metal materialensures conductivity to the activated carbon layer in the capacitor oractive substance in the battery, and also enhances strength of joiningto the activated carbon layer or positive electrode.

[0031] More particularly, the metallic surface of the valve metalmaterial may be coated with a passive film. In this case although themetallic surface of the valve metal material itself may loseconductivity, the metallic surface is prevented stably from oxidationbecause of no contact with the electrolyte, and the valve metal materialhas stable conductivity via the carbon particles for extended periods of

[0032] The valve metal material in accordance with the present inventioncan be formed into sheet. The term “sheet” herein refers to plate,sheet, film and foil. The valve metal material may be formed of productsother than sheet, having a small thickness with a desired shape. Theelectrode metal material may have a shape of net or punched plate. thismay be is adequate to apply, for example, the positive electrode thereonto produce non-aqueous secondary battery.

[0033] The sheet and other formed products may include carbon particlesat least on one side thereof and also may include carbon particles onboth sides thereof.

[0034] A method of producing a valve metal material for electrodes inaccordance with the present invention contains driving or squeezingnumerous carbon particles into the surface thereof. Pressing using diesor rolling using rollers may be employed to drive powder of carbonparticles into a valve metal sheet, then, carbon particles being fixedin the surface of the valve metal sheet with the particle exposed on thesurface.

[0035] Another method may be adopted where a slurry of carbon particlesis applied and dispersed on a surface of a valve metal material andpressed to squeeze the carbon particles into the surface, then,obtaining carbon-containing electrode metal material. The carbon slurrymay comprise carbon particles and a solvent, particularly, volatiledispersing liquid without any binder used. The dispersing liquid may bewater, alcohol or other volatile liquid because after drying, it ispreferable that only carbon particles remain dispersed on the surfacewithout containing any impurity such as binder solid.

[0036] Prior to pressing in the above methods, the valve metal materialmay preferably be roughened on the surface, particularly be made porousin a thin layer of the surface, facilitating carbon particles to engageand embed in the porous surface layer effectively.

[0037] Also, a method of producing the valve metal material forelectrodes in accordance with the present invention may include a stepwherein the powder material for the valve metal and carbon particles aresemi-melted in a mixture condition and subjected to pressure so as to beformed into a dense metal ingot. The metal ingot, including carbonparticles dispersed inside, is forged or rolled into a product having adesired shape, and then the carbon particles are exposed to the surfaceof the product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be described below in detail referringto the accompanying drawings, in which:

[0039]FIG. 1 is a schematic sectional view showing an example of acarbon-containing valve metal material in accordance with the presentinvention, wherein carbon particles are fixed in the surface of thevalve metal sheet;

[0040]FIG. 2 is a schematic sectional view showing another example of acarbon-containing valve metal material in accordance with the presentinvention;

[0041]FIG. 3 is a schematic sectional view showing still another exampleof a carbon-containing valve metal material in accordance with thepresent invention;

[0042]FIG. 4 is a schematic sectional view showing yet still anotherexample of a carbon-containing valve metal material in accordance withthe present invention, wherein carbon particles are fixed on both sidesof the valve metal sheet;

[0043]FIG. 5 is a schematic partially-sectional view showing adouble-layer electrode used for an electric double-layer capacitorformed of the carbon-containing valve metal material in accordance withthe present invention;

[0044]FIG. 6 is a schematic partially-sectional view showing adouble-layer electrode used for a conventional electric double-layercapacitor;

[0045]FIG. 7 is a schematic partially-cutaway perspective view showing awinding type electric double-layer capacitor;

[0046]FIG. 8 is a schematic partially-sectional view showing adouble-layer electrode used for a button-type electric double-layercapacitor formed of the carbon-containing valve metal material inaccordance with the present invention;

[0047]FIG. 9 is a schematic sectional view showing the button-typeelectric double-layer capacitor;

[0048]FIG. 10 is a schematic partially-cutaway perspective view showingthe button-type electric double-layer capacitor.

[0049]FIG. 11 shows a schematic partial cross sectional view of anon-aqueous secondary battery; and

[0050]FIG. 12 shows a cross sectional structure of a positive electrodefor a non-aqueous secondary battery which is formed on both sides of ancarbon containing electrode metal material according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0051] A valve metal material for electrodes in accordance with thepresent invention includes carbon particles fixed on the surface thereofas described above. The valve metals can be selected from among metalscapable of forming a passivated layer on the surface thereof. Forexample, such valve metals may include tantalum, aluminum, titanium,niobium, zirconium, bismuth, silicon and hafnium. Alternatively, thevalve metal can be selected from among alloys including these elementscapable of generating a valve action, such as for example, atitanium-based alloy including boron and tin, a titanium-based alloyincluding chromium and vanadium, a titanium-based alloy includingvanadium and antimony, and an aluminum-based alloy including titanium.The most desirable material is aluminum, in particular, high-purityaluminum.

[0052] The electrode metal material of the present invention is formedinto the form having a desired thickness, for example, into sheet. Thethickness of the sheet may be in a range of 10 μm to 5 mm, although thethickness depends on the kind of capacitor or battery, or the kind ofelectrode. Generally, for winding type electric double-layer capacitorsand electrolytic capacitors, metal foil having a thickness of 50 to 500μm is preferably used to provide flexibility and sufficient windingturns. On the other hand, for button-type electric double-layercapacitors, the valve metal material, when also used as a part of thewall or bottom portion of the container, should preferably have a largerthickness of about 0.50 to 3.0 mm, for example, to provide strength tothe wall or bottom portion.

[0053] A base metal plate for providing strength may be cladded with theabove-mentioned thin valve metal material, and carbon particles may beincluded in the clad valve metal material used. A highlycorrosion-resistant metal or alloy, such as nickel or stainless steel,may be used as this kind of base metal. Such base metal plate claddedwith valve metal material may used for a casing which also supports apositive electrode of button-or coin-type secondary batteries.

[0054] On the other hand, carbon particles are formed of conductivecarbon particles, such as graphite or carbon black. Carbon black as anexample may be acetylene black. Furthermore, carbon particles may beparticles of activated carbon.

[0055] The diameter of carbon particles should preferably be in therange of 0.01 to 50 μm, more preferably, in the range of 0.1 to 10 μm.In addition, the carbon particles can have one of particulate, granularand fibrous forms. In the case of fibrous carbon particles, theabove-mentioned particle diameter in the range of 0.1 to 50 μm refers tothe fiber length thereof.

[0056] The content of carbon particles should preferably be in a rangeof 1 to 90% of the area percentage of the carbon with respect to thewhole surface area of the valve metal material. If the area percentageof the carbon is less than 1%, it may be difficult to sufficientlyreduce contact resistance at the surface. The area percentage of thecarbon should preferably be higher. However, if the area percentage ofthe carbon is more than 90%, it becomes difficult to stably hold carbonparticles pressed into the surface of the valve metal by a press method.Accordingly, the area percentage of the carbon particles on the surfaceshould preferably be in a range of 5 to 60%, more preferably, in a rangeof 10 to 40%.

[0057] The valve metal material should preferably have a rough surface.In particular, carbon particles should preferably project slightly fromthe surface of the metal material. The projection of the carbonparticles can be performed by subjecting the surface to electrolyticetching in an acidic aqueous solution. The exposure of numerous carbonparticles can increase contact frequency to an activated carbon layerfor an electric double-layer electrode structure. Furthermore, theactivated carbon layer can be firmly fixed by an anchor effect. Also,the exposed carbon particles from the electrode can increase contactfrequency to active substance contained in the positive electrode ofnon-aqueous secondary batteries.

[0058]FIG. 1 shows a carbon-driven metal material 1 wherein nearlyparticulate carbon particles 2 are driven on one side of a sheet ofvalve metal material 10. This figure shows a schematic view of anexample of the valve metal material in which the carbon particles 2 arepartially embedded in the surface of the metal material and the upperportions thereof project from the surface.

[0059]FIG. 2, similar to FIG. 1, is a conceptual view showing acondition wherein the carbon particles 2 are crushed and wholly embeddedin the surface of the metal material. However, in the carbon-drivenmetal material 1, the surfaces of the carbon particles are still exposedto the surface of the metal material, and the carbon particles can beused to ensure conductivity. This condition may be obtained whenrelatively soft carbon particles are pressed strongly.

[0060]FIG. 3 is a view showing a condition wherein the carbon-drivenmetal material 1 shown in FIG. 2 is subjected to electrolytic etching toremove its metallic surface 11, thereby allowing the carbon particles toproject from a etched surface. FIG. 4 is a view showing a conditionwherein the carbon particles driven on both sides of the sheet of thevalve metal material which sides are subjected to etching, therebyallowing the carbon particles to project from both etched surfaces.

[0061] Furthermore, the whole surface of the carbon-containing metalmaterial may be roughened by blasting. Blasting makes the surface of thevalve metal material rough directly, and the carbon particles expose. Inaddition, for electric double layer capacitors, the activated carbonlayer can be fixed firmly to the roughened surface, and the contactresistance of the surface can be reduced.

[0062] A passive film my preferably be formed on the surface of thecarbon-containing metal material (for example, the metallic surface 11shown in FIGS. 3 and 4). Even if water is present in electrolyte whilethe valve metal material is used as an electrode, the passive filmprotects the surface of the valve metal material against oxidation andcorrosion. Therefore, the electrodes can be stabilized further, withoutadversely affecting the conductivity thereof due to the existence of thecarbon particles.

[0063] The passive film may have only a thickness capable ofwithstanding working voltage of a capacitor comprising the film. Forexample, in the case of an electric double-layer capacitor rated at 2.5Vto 3.5V, the film should only have a thickness capable of withstanding avoltage in the range of 4 to 5 V. In this case, the valve metal materialis provided with a passive film having a thickness of 40 Å to 60 Å ormore. Also, for the positive active electrode of non-aqueous secondarybatteries, the passive film formed on the carbon containing electrodemetal material may have higher withstand voltage than 3V, preferably of4 to 5V.

[0064] With respect to lithium ion secondary batteries, FIG. 11 shows awinding-type lithium ion secondary battery, in which a pair ofelectrodes i.e., a positive electrode 35 and a negative electrode 37,between which a separator 5 is inserted, are wound, penetrated with annon-aqueous electrolyte in a casing 71 for sealing.

[0065] An electrode metal material of the present invention is used toform the positive electrode 35 which comprise an mixture of positiveactive substance, conductive material and a binder which is formed onboth sides of the electrode metal material. The positive activesubstance may be a compound capable of absorbing and emitting any ionsof H⁺, Li⁺, Na⁺ and K⁺, preferably, oxides or chalcogenides oftransition metals, or carbon, particularly, lithium-containingtransition metal oxides. The transition metal may be one or moreselected from a group of Co, Ni, Fe, V and Mn. A conductive material maybe an electron-conductive material not to chemically react in thebattery, such as natural graphite, synthetic graphite, carbon black,acetylene black or carbon fibers. As a binder, polysaccharides,thermo-plastic resins or rubber-like elastic polymers may be used. Abinder may include starch, polyvinylalcohol, carboxylmethylcellulose,hydroxy-propylcellulose, polyflorovinylidene, etc.

[0066] An electrolyte comprises an organic solvent and a salt soluble tothe solvent to dissociate. A solvent may be one or a mixture ofpropylene carbonate, ethylene carbonate, tetrahydrofuran,2-methyltetrahydrofuran, γ-butyrolactone, and 1,2-dimethoxyethane. Thesalt as an electrolytic substance may be selected from LiPF₆, LiClO₄,LiBF₄ and LiCF₃SO₃.

[0067] The separator 5 may be thin insulating material capable ofpenetrating an electrolyte therethrough such as polypropylene porousfilm, woven or unwoven glass cloth, paper made of manila paper andrayon.

[0068] In this battery structure, FIG. 12 shows a cross sectionalstructure of a positive electrode 35 for a non-aqueous secondary batterywhich is formed on both sides of an carbon containing electrode metalmaterial 1 according to the present invention. Since the electrode metalmaterial 1 of the present invention which supports the positiveelectrodes 35 is provided with carbon particles on its surface, thecarbon particles 2 can effectively connect the electrode metal material1 of a valve metal 10 directly with a positive electrode 35 effectivelyeven though a thin insulating film 4 has been formed in interfacesbetween the metallic surface of the electrode metal material 1 and thepositive electrode 35 by oxidation of the metallic surface of theelectrode material metal. This results in reduction in equivalent seriesresistance and capacity loss of batteries.

[0069] Some methods may be adopted to produce an electrode metalmaterial formed of a valve metal material containing numerous carbonparticles at least in the surface thereof.

[0070] In a first method, a mixture of valve metal powder and carbonpowder is heated near its melting point and pressurized in a containerto make an ingot so that the carbon powder may be contained in the valvemetal ingot. This method further includes a step of subjecting the ingotof carbon-containing valve metal produced by the above step to plasticworking in order to obtain a desired shape of the valve metal material.In the plastic working step, hot or cold forging or rolling can beutilized, whereby forming sheet or foil having a desired thickness or aformed product having any other shapes.

[0071] A second method includes a carbon-powder driving step whereincarbon particles are driven into the surface of a valve metal materialby pressurizing carbon particles dispersed on the surface of the valvemetal material.

[0072] The carbon particle driving step in the second method can also beaccomplished by a press technique where dies are used to press and fitcarbon particles into the surface of the valve metal material. The diesmay have a flat, hardened plate or the like.

[0073] Furthermore, the carbon particle driving step can also beaccomplished by a rolling method wherein rollers are used to drivecarbon particles into the surface of the valve metal material. In eitherof the two methods, carbon particles can be pressed and fitted in thesurface of the valve metal material and fixed.

[0074] By using the second method, carbon particles are driven in thesurface of the valve metal material having a desired thickness. Theabove-mentioned carbon particle driving step can be performed byapplying a surface pressure of 0.5 to 10000 kg/cm² in a directionperpendicular to the surface of the metal material. This pressure isdetermined depending on the hardness of the surface of the valve metalmaterial and the hardness and particle size of the carbon particles.

[0075] Furthermore, the carbon particle driving step may also be used asa step of pressing or forging a valve metal blank into a formed producthaving a desired shape. In other words, in this case, the carbonparticle driving step is carried out when the valve metal ingot is hotor cold worked. In this step, just when the valve metal material ispressurized by hot or cold forging or rolling, the carbon particles aredriven into the forged or rolled surface.

[0076] Prior to the carbon particle driving step, numerous carbonparticles are dispersed on the surface of a valve metal material, forexample, in the form foil, sheet or plate. Usually, carbon powder may bepowdered on the surface.

[0077] Preferably, a slurry containing carbon particles and liquid maybe applied on a surface of a valve metal material, facilitate thedispersing Of carbon particles. The liquid in the slurry may be avolatile dispersing liquid to facilitate dehydration of the slurry. Theslurry may not contain a binder which remain in a powder after drying.The dispersing liquid may be water, alcohol or other volatile liquidbecause after drying, it is preferable that only carbon particles remaindispersed on the surface without containing any impurity such as bindersolid. Preferably, the carbon slurry may be dried on the surface of thevalve metal material, and in the carbon particle driving step, ispressed to squeeze the carbon particles into the surface, obtainingcarbon-containing electrode metal material.

[0078] Prior to pressing in the above methods, the valve metal materialmay preferably be roughened on the surface, allowing carbon particles toengage and embed easily on the rough surface.

[0079] A technique for roughening a surface includes blasting sand orother harden powder onto the surface. Other roughening method includeschemical or electrolytic etching which makes the surface porous in athin layer under the valve metal surface. By this etching, a greatnumber of pores are produced opening to the surface of the valve metalmaterial and extending in some depth under the surface and disperseduniformly in an area of the surface.

[0080] Such a roughened or porous surface may easily receive and holdthe applied carbon powder or dried carbon slurry on the surface,preventing the carbon particles to be sent flying. Roughening of a valvemetal surface can eliminate the need for use of any binder mixing in thecarbon slurry, avoiding impurity inclusion on the carbon embeddedsurface.

[0081] Particularly, the porous surface layer formed by etching is easyto be deformed by pressing or rolling on the surface, allowing carbonparticles to be embedded easily in high carbon density into thesurface-deformed layer from the porous surface layer during pressing orrolling.

[0082] The roller used in rolling may be an roller embossed on itssurface. The embossed roller can make an embossed pattern on the carbonembedded surface at the same time during driving carbon particledriving.

[0083] Furthermore, in the method in accordance with the presentinvention, the surface of the carbon containing metal material maypreferably be coarsened after the carbon particle driving step.

[0084] For this purpose, it is desired that, after the carbon particledriving step, the method includes a step of exposing the carbonparticles to the surface by electrolytically etching in an acidicaqueous solution. By this treatment, the carbon particles exposed on thesurface project from the surface and carbon particles slightly embeddedbelow the surface also are exposed to the surface. The exposure ofnumerous carbon particles can increase the contact frequency of anactivated carbon layer for an electric double-layer electrode structure.Furthermore, the activated carbon layer can be firmly fixed by an anchoreffect.

[0085] After the carbon particle driving step, the method may includeblasting as a step of exposing carbon particles to the surface. Thisblasting technique can also accomplish direct roughing of the surfaceand exposing of the carbon particles by blasting.

[0086] The production method may preferably include a step of forming apassive film on the metallic surface of the carbon containing metalmaterial after the carbon particle exposing step. Formation of thepassive film may use a technique of heating the carbon-containing metalmaterial oxidized in an oxidative atmosphere, such as in air. The heattreating is performed at 300°-620° C.

[0087] Alternatively, another method is used, wherein thecarbon-containing metal material is anodized using anodic oxidation of ametallic surface of the valve metal.

[0088] The passive film should have a thickness capable of withstandingan applied voltage of 4 to 5 V in the case of an electric double-layercapacitor rated at 2.5 to 3.5 V, for example. In this case, the valvemetal material is provided with a passive film having a thickness of 40Å to 60 Å or more.

[0089] Capacitors in accordance with the present invention includeelectric double-layer capacitors and electrolytic capacitors. In bothtypes of the capacitors, non-aqueous electrolyte is used, and the valvemetal material thereof makes contact with the electrolyte.

[0090]FIG. 7 is a schematic view showing a winding type capacitor usedas a kind of electric double-layer capacitor. The winding type capacitoris provided with flexible electric double-layer electrodes. Theelectrode comprises thin valve metal foil used as a valve metalmaterial, and activated carbon layers bonded to both sides of the foil.Numerous carbon particles are fixed on the surface of the foil so as toexpose, thereby making contact with the activated carbon layers.

[0091] A pair of electric double-layer electrodes, holding a separatortherebetween, is wound to a coil and enclosed in a container while beingimmersed in non-aqueous electrolyte, thereby forming an electricdouble-layer capacitor. The electrolyte is formed of an organic solventnot including water and a salt dissolved in such a solution so as to bedissociated. A solution wherein tetraethyl ammonium perchlorate used asan electrolyte is added to propylene carbonate used as a solvent istaken as an example.

[0092] The activated carbon layer is formed in a thin film by formingactivated carbon powder into a paste form and by applying the paste tothe surface of the valve metal foil. The paste is obtained, for example,by kneading a mixture of activated carbon powder, conductive carbonpowder and an appropriate binder, such as cellulose or fluororesin, asnecessary, together with water or other solvent. The coated paste filmis appropriately dried and heated together with the valve metal foil tocure the binder, whereby the film is fixed to obtain an electricdouble-layer electrode.

[0093] Leads are connected to the pair of electric double-layerelectrodes, one lead to each electrode. Furthermore, the electrodes werewound while holding a separator therebetween so as to be formed into acoil. The separator is formed of an appropriate thin material that isinsulating and water-permeable, such as glass-fiber woven or non-wovencloth.

[0094] The coil comprising the electric double-layer electrodes and theseparator is immersed in electrolyte and accommodated in a metalcontainer having a bottom. The opening of the container is sealed with asealing material. The leads pass through the sealing material and areextended outside.

[0095] With the above-mentioned structure of the electrode, even when athin insulating film 4 is present at the interface between the foil-likemetal material 10 of the electrode metal material 1 and the polarizableelectrode 30 of the electric double-layer capacitor as shown in FIG. 5,no oxidized film is formed on the surfaces of carbon particles 2 exposedfrom the electrode foil 10. For this reason, electric conduction can bemaintained by the carbon particles 2 at portions wherein the carbonparticles 2 are present. As a result, the equivalent series resistance(ESR) of the electric double-layer capacitor decreases, and theconduction portions increase in number, whereby the capacitance thereofincreases.

[0096]FIGS. 9 and 10 show a button-type electric double-layer capacitor.An activated carbon layer 30 is bonded to a disc-like sheet 10 formed ofthe valve metal material of the present invention via an adhesive layer9, thereby forming a pair of double-layer electrodes 3. The twodouble-layer electrodes 3 are disposed face-to-face with an insulatingseparator 5 therebetween, and accommodated inside a metal containercomprising two mating portions 60 and 61.

[0097] The valve metal material sheets 10 and 10 of the two double-layerelectrodes 3 and 3 are joined to the inner surface sides of the bottomportion 60 and the lid portion 61 of the metal container, respectively.The bottom portion and the lid portion are then joined to each other attheir peripheral portions so as to be watertight via an insulating ringpacking 69. The container is filled with non-aqueous electrolyte so thatthe double-layer electrodes and the activated carbon layers aresufficiently immersed in the electrolyte. The non-aqueous electrolytemay be, for example, a solution of tetraethyl ammonium perchlorate usedas an electrolyte in propylene carbonate used as a solvent, as describedabove.

[0098] Double-layer electrodes 3 for the button-type electricdouble-layer capacitor are shown in FIG. 8. The activated carbon layer30, i.e., the polarizable electrode 30, is formed of a sheet made ofactivated carbon particles or fibers.

[0099] For example, the activated carbon layer 30 is obtained asdescribed below. A paste is prepared by mixing activated carbon powder,a solvent and an appropriate binder, and this paste is formed into thinfilm, which are dried and cured to obtain sheets including activatedcarbon particles. The sheets are used as the activated carbon layer 30.

[0100] The sheet of activated carbon fiber is formed of fiber activatedat the carbonization step of phenol-based resin fiber, for example. Theactivated carbon fiber is woven into a sheet.

[0101] The above-mentioned activated carbon particle sheet or theactivated carbon fiber sheet is stamped into sheet pieces having adesired shape, and the sheet pieces are bonded to the carbon-containingside of the valve metal material sheet so as to be assembled into thedouble-layer electrode 3. An organic adhesive 9, being conductive, isusually used for the bonding.

[0102] The conductive adhesive may be used to firmly bond a sheet ofchemically active carbon fiber or the like to the valve metal materialsheet. Furthermore, the adhesive 9 is used to electrically connect thecarbon particles on the valve metal material side to some parts of thefiber and particles on the activated carbon side. The carbon particles 2on the valve metal material side ensures conductivity at thedouble-layer electrode 3 via the adhesive layer 9, thereby reducing theinternal resistance of the capacitor used as a power source.

[0103] The present invention also includes a non-aqueous electrolyticcapacitor having a cathode formed of the sheet of valve metal material.The anode of the electrolytic capacitor is formed of a valve metal sheetprovided with an insulating, very thin, highly dielectric layer on thesurface thereof. The cathode thereof is formed of a valve metal sheetincluding carbon particles on the surface thereof. Both the sheets ofthe anode and the cathode, disposed face-to-face, are wound orintegrated, and they are accommodated in a container and immersed intoelectrolyte inside the container.

[0104] The electrolyte of this electrolytic capacitor is prepared byadding, for example, an appropriate inorganic or organic salt to anethylene glycol-based solvent. Even if a small amount of water ispresent in the electrolyte, only the metallic surface of the valve metalmaterial is oxidized, whereby the carbon particles hold contact with theelectrolyte to ensure conductivity. For this reason, the electrolyticcapacitor is far less likely to decrease in resistance, and the internalresistance thereof is far less likely to increase even after use forextended periods of time.

EMBODIMENTS [EXAMPLE 1]

[0105] A valve metal was formed of high-purity aluminum foil offour-nine grades, having a thickness of 20 μm. An electrode metalmaterial was produced as described below. Acetylene black particleshaving an average particle diameter of 2 μm were dispersed uniformly onthe surface of the metal foil in an amount of 50% by weight with respectto the metal foil per unit area of the foil, and subjected to a linepressure of 100 kg/cm² in a direction perpendicular to the surface ofthe foil by using reduction rollers. As a result, carbon-embedded metalfoil, wherein numerous carbon particles were driven in the surface ofthe aluminum foil, was obtained.

[EXAMPLE 2]

[0106] In the same way, an electrode metal material was produced asdescribed below. Acetylene black particles having an average particlediameter of 2 μm were dispersed uniformly on the surface of high-purityaluminum foil of four-9 grade, having a thickness of 20 μm, at 50% byweight in the same way as described above, and subjected to a linepressure of 100 kg/cm² in a direction perpendicular to the surface ofthe foil by using rollers. Numerous carbon particles were thus driven inthe surface of the aluminum foil. After this, the carbon-embedded metalfoil was subjected to electrolytic etching in a nitric acid-basedetching solution to expose the carbon particles to the surface.

[EXAMPLE 3]

[0107] In the same way, phenol-resin-based activated carbon particleshaving a particle diameter of 10 μm were dispersed uniformly on thesurface of etched high-purity aluminum foil of four-9 grade, having athickness of 20 μm, which is used as a valve metal material, and thensubjected to a pressure of 100 kg/cm² in a direction perpendicular tothe surface of the foil by using reduction rollers. As a result,numerous carbon particles were driven in the surface of the aluminumfoil. After this, the carbon-embedded metal foil was subjected toblasting to expose the carbon particles to the surface.

[0108] Electric double-layer capacitors were assembled by using thesepieces of carbon-embedded metal foil for electrodes in accordance withExamples 1 to 3. To form a double-layer electrode, the carbon-embeddedmetal foil was coated with a paste including activated carbon particles.To prepare the paste, after obtaining a powder mixture ofphenol-resin-based activated carbon particles having a particle diameterof 5 μm, an ammonium salt of carboxymethyl cellulose(C₆H₉O₅CH₂CO₂NH₄)_(n) and acetylene black in a weight ratio of 60.2:2,methanol three times as much as the powder mixture and water five timesas much as the powder mixture by weight were added to the powder mixtureand kneaded. The electrode metal material foil was immersed in thispaste for 15 seconds, whereby a film of the paste was formed on themetal foil 1. The foil was then dried for 1 hour at 100° C. in the airto form an activated carbon layer (polarizable electrode). Next, thefoil was cut and divided into two sheets, each having dimensions of25×400 mm, thereby obtaining a pair of double-layer electrodes.

[0109] Next, aluminum leads 6 were connected to the double-layerelectrodes, one lead-to each electrode. The two double-layer electrodeswere disposed face-to-face with a separator 5 therebetween, and thenwound and formed into a coil. The coil was immersed into electrolytewherein tetra ethyl ammonium perchlorate was added to propylenecarbonate in a ratio of 0.5 mol/litter, and vacuuming was carried out,whereby the double-layer electrodes 3 and the separator 5 wereimpregnated with the electrolyte. The double-layer electrodes 3 and theseparator 5 were then inserted into an aluminum case 7, and the case 7was sealed with a packing, whereby an electric double-layer capacitorwas obtained.

[EXAMPLE 4]

[0110] Just as in the case of Example 1, a valve metal material wasformed by press-fitting carbon particles in the surface thereof. Thevalve metal material was electrolytically etched in a nitric-acid-basedetching solution to expose the carbon particles to the surface thereof,and then subjected to oxidation at 400° C. for 2 minutes in the air.

[0111] Just as in the case of Example 1, an activated carbon layer wasformed on the surface of the valve metal material to obtain adouble-layer electrode. By using the electrodes, an electricdouble-layer capacitor was obtained.

[EXAMPLE 5]

[0112] Just as in the case of Example 3, a valve metal material wasformed as described below. Phenol-resin-based activated carbon particleshaving a particle diameter of 10 μm were dispersed uniformly on aluminumfoil having a thickness of 20 μm, and the foil was subjected to blastingto expose the carbon particles to the surface thereof.

[0113] To form double-layer electrodes, valve metal material foil wascoated with a paste. To prepare the paste, after obtaining a powdermixture of phenol-resin-based activated carbon particles having aparticle diameter of 5 μm, an ammonium salt of carboxymethyl celluloseand acetylene black in a weight ratio of 60.2:2, methanol three times asmuch as the powder mixture and water five times as much as the powdermixture by weight were added to the powder mixture and kneaded. Theelectrode metal material foil was immersed in the paste for 15 seconds,whereby a film of the paste was formed on the metal foil 1. After this,the foil was dried for 1 hour at 180° C. in the air to form an activatedcarbon layer (polarizable electrode). The foil was then cut to divideinto two sheets, each having dimensions of 25×400 mm, thereby obtaininga pair of double-layer electrodes. Next, just as in the case of theabove-mentioned examples, the double-layer electrodes were used toassemble an electric double-layer capacitor.

[EXAMPLE 6]

[0114] Just as in the case of Example 3, a valve metal material ofaluminum foil with a thickness of 20 μm, on which phenol-resin-basedactivated carbon particles having a particle diameter of 10 μm weredispersed uniformly, was subjected to blasting to expose the carbonparticles on the surface. Furthermore, this valve metal material wassubjected to an oxidizing treatment at 400° C. for 2 minutes in the air.

[0115] The foil of the carbon-containing valve metal material obtainedas described above was coated with a paste to form double-layerelectrodes. The paste was prepared by kneading a powder mixturecomprising phenol-resin-based activated carbon fiber having been cut toa length of 5 μm in the long-chain direction thereof, an ammonium saltof carboxymethylcellulose and acetylene black in a weight ratio of60.2:2, respectively, together with methanol three times as much as thepowder mixture and water five times as much as the powder mixture byweight added to the powder mixture. The electrode metal material foilwas immersed in the paste for 15 seconds, whereby a film of the pastewas applied on the metal foil 1. The foil was then dried for 1 hour at180° C. in the air to form an activated carbon layer. The foil was thencut and divided into two sheets, each having dimensions of 25×400 mm,thereby obtaining a pair of double-layer electrodes. Next, just as inthe case of the above-mentioned examples, an electric double-layercapacitor was obtained.

[EXAMPLE 7]

[0116] Just as in the case of Example 1, a valve metal material wasobtained by using aluminum film having a thickness of 20 μm, on whichphenol-resin-based activated carbon particles having a particle diameterof 10 μm were dispersed uniformly.

[0117] To prepare a mixture powder for a paste, a powder mixture ofphenol-resin-based activated carbon fiber having been cut to a length of5 μm in the long-chain direction thereof, an ammonium salt ofcarboxymethylcellulose and acetylene black in a weight ratio of 60.2:2was used. To this powder mixture, methanol three times as much as thepowder mixture and water five times as much as the powder mixture byweight were added in order to prepare a mixture solution in slurry form.A collector 1 was then immersed in the mixture solution for 15 seconds,whereby a polarizable electrode 3 was formed as a film on the collector1. Next, the electrode was dried for 1 hour at 180° C. in the air, andthe foil was cut and divided into two sheets, each having dimensions of25×400 mm, thereby obtaining a pair of double-layer electrodes. Just asin the case of the above-mentioned examples, an electric double-layercapacitor was obtained.

[Comparative example]

[0118] Electrode metal material foil was formed of high-purity aluminumfoil of four-9 grade, having a thickness of 20 μm and not includingcarbon particles. This valve metal material was immersed in a watersolution of 1.0 N hydrochloric acid, 6.0 N nitric acid and 4.0 Nphosphoric acid. The aluminum foil was subjected to etching by applyingdirect current to the foil used as the anode. An electric double-layercapacitor was obtained just as in the case of Example 1.

[0119] The capacitors in accordance with these examples and thecomparative example were charged at a constant voltage of 2.5 V for 1hour. The capacitors were then discharged at a constant current of 100mA, and the capacitance C and equivalent series resistance (ESR) valuesof the capacitors were measured. Furthermore, the capacitors werecharged at a constant voltage of 2.8 V at 75° C. in a constanttemperature bath, and maintained in these conditions for 3000 hours.They were then discharged at a constant current of 100 mA, and thecapacitance C and equivalent series resistance (ESR) values weremeasured in the same way. Table 1 shows the results of the measurements.TABLE 1 C ΔC ESR ΔESR Surface treatment (F) (%) (mΩ) (%) Example 1Carbon-embedding 27 −16.1 55 16.5 Example 2 Carbon-embedding, 42 −5.5 284.0 etching Example 3 Carbon-embedding, 48 — 32 — blasting Example 4Carbon-embedding, 40 −3.0 30 2.5 etching, oxidation Example 5Carbon-embedding, 48 −6.2 32 4.5 blasting, oxidation Example 6Carbon-embedding, 45 −3.0 34 2.8 blasting, oxidation Example 7Carbon-embedding 35 −18.5 60 14.8 Comparative — 20 −27.5 80 22.0

[0120] The ΔC and ΔESR in Table 1 represent the change ratios of C andESR from the initial C and ESR values to those obtained 3000 hours aftertreatments in the above-mentioned conditions, respectively.

[0121] As clearly disclosed in Table 1, it is understood that thecapacitance values of the electric double-layer capacitors formed of thecarbon-containing metal materials in accordance with the examples arelarger than that of the comparative example, and that the ESR values ofthe former are smaller than that of the latter. This can be explained asfollows: by using electrode foil to which carbon particles are added,the carbon particles are exposed to the surface of the electrode foil,whereby conductivity can be maintained at the interface between theelectrode foil and the polarizable electrode. Furthermore, according tothis table, it is found that the stability of capacitance and ESR withrespect to time can be enhanced by making the surface of thecarbon-containing metal material rough by carrying out etching orblasting, in particular, by carrying out oxidization to form a passivefilm.

[0122] A further embodiment of the invention is shown below with respectto use of carbon slurry in the method producing an electrode metalmaterial.

[EXAMPLE 8]

[0123] Aluminum of four-nine grade having 20 μm thick, was etched toproduce a great number of pores opening to the surface, and was used toapply a carbon slurry of formulation of 1 part of carbon particles, 2parts of ethanol and 20 parts of water. In this Example, acetylene blackof mean particle size of 0.2 μm was used as carbon particles. Thealuminum foil is soaked into the slurry for 10 seconds to produce aslurry film on the surface, dried in air 30 minutes, and then rolledover the dried slurry by pressurizing at 100 kg/cm of line pressure,obtaining a carbon embedded metal sheet.

[EXAMPLE 9]

[0124] In this Example, activated carbon powder from phenol resin having2 μm of mean particle size was used to produce carbon embedded metalsheet, but other conditions were similar to Example 8.

[EXAMPLE 10]

[0125] Part of the carbon embedded metal sheet from Example 8 waselectrolytically etched in a nitrate etching solution to expose carbonparticles on the surface and then oxidized by heating at 400° C. for 2minutes in air.

[EXAMPLE 11]

[0126] Part of the carbon embedded metal sheet from Example 9 wasblasted to expose carbon particles on the surface and then oxidizedsimilarly to Example 10.

[Comparative 2]

[0127] A aluminum foil was used without applying carbon particles for anelectrode metal material.

[Comparative 3]

[0128] A aluminum foil without applying carbon particles was oxidized byheating at 400° C. in air and used for a electrode metal material.

[0129] The carbon embedded metal sheets from these Examples 8-11 and thecomparative sheets were provided for fabricating electric double-layercapacitors. The carbon embedded metal sheets were applied with anactivated carbon past which was formed of a powder of activated carbonfrom phenol resin ammonium carboxylmethylcellulose and acetylene blackby soaking and than dried, obtaining activated carbon laminate. thelaminate was cut to two pieces of strips of 25 mm wide and 400 mm longas electric double layer electrodes. The two pieces of electrodes 3 and5 were wound with a separator 5 to a coil, impregnated with anelectrolyte containing tetraethyl ammonium perchlorate and propylenecarbonate and contained in a casing 7, obtaining electric double layercapacitors.

[0130] The electric double layer capacitors were tested by charging atconstant 2.5V for 1 hour and discharging 100 mA of current to measuredielectric capacitance and ESR. thereafter, The same capacitors werecharged at constant 2.8V at 75° C. maintained 3000 hours, and dischargedin constant 100 mA of current, and dielectric capacitance and ESR weremeasured. The results are shown in Table 2. TABLE 2 C ΔC ESR ΔESRSurface treatment (F) (%) (mΩ) (%) Example 8 carbon slurry 42 −2.5 362.9 oxidation Example 9 carbon slurry 40 −3.0 38 3.5 oxidation Example10 carbon slurry oxidation 48 −1.2 30 1.9 etching Example 11 carbonslurry oxidation 45 −1.6 32 2.2 blasting Comparative 2 nocarbon-embedding, 25 −17.0 75 16.5 Comparative 3 No carbon-embedding, 12−10.0 93 8.2 oxidation

[0131] It is found from Table 2 that the capacitors using the carbonbedded metal material as supports for carbon electrodes are higher incapacitance and lower in ESR than Comparative examples using no carbonparticles. Treatment of etching or blasting and particularly passivationof a metallic surface by oxidation are useful to increase Dielectriccapacity and ESR stability.

[0132] A further embodiment of the invention is shown below with respectto application to lithium ion non-aqueous batteries.

[EXAMPLE 12]

[0133] Carbon-embedded metal foil having numerous carbon particlesdriven in the surface of the aluminum foil was obtained in the similarmanner to Example 1, except that the acetylene black particles weredispersed in an amount of 30% by weight, aluminum foil having 50 μm. Thecarbon embedded alumina foil was electrolytically etched with a nitrateetchant to expose the carbon particles on the etched surface.

[EXAMPLE 13]

[0134] part of the aluminum foil obtained in Example 12 was furtheranodized in an ammonium adipate solution applying 5v to producesupporters for positive electrode.

[EXAMPLE 14]

[0135] Aluminum foil of four-nine grade having 10 μm was embedded withnumerous carbon particles in a similar manner to Example 12, claddedonto both sides of a piece of stainless steel foil of 10 μm inthickness, and then, electrolytically etched with a nitrate solutionexpose the carbon particles from the etched surface.

[EXAMPLE 15]

[0136] part of the carbon embedded aluminum foil obtained in Example 14was anodized in the same way as Example 13 to produce supporters forpositive electrode.

[EXAMPLE 16]

[0137] Aluminum foil of four-nine grade having thickness of 10 μm wasclad with both surfaces of a piece of stainless steel foil and carbonparticles were dispersed uniformly on the aluminum foil in an amount of25% by weight with respect to a unit area of the aluminum foil andpressed with a line pressure of about 100 kg/cm by using rollers for acold rolling mil, then being embedded into the both surfaces of thealuminum foil. The carbon embedded clad foil obtained was etched byusing a nitrate solution etchant as noted above Example 14 to expose thecarbon particles from the etched surfaces of the aluminum foils,producing a supporter for positive electrode.

[EXAMPLE 17]

[0138] Part of carbon embedded material of clad aluminum and stainlesssteel was anodized in ammonium adipate solution applying 5v as shown inExample 15 to produce supporters for positive electrode.

[0139] The supporters from these Examples 12-17 were supplied tofabricate lithium ion secondary batteries, wherein a slurry was preparedcontaining 90% by weight of LiCoO₂ as positive active substance, 7% byweight of acetylene black as conductive material, and 1% by weight ofcarboxylmethylcellulose and 2% by weight of polyfluorovinylidene, andapplied on both sides of the carbon embedded aluminum foil as aelectrode metal material, and then, dried in air and pressed to make apositive electrode in thickness of 0.03 mm.

[0140] On the other hand, a negative electrode was produced of a slurryincluding 94% by weight of graphite, 2% by weight ofcarboxylmethylcellulose and 4% by weight of styrenebutadiene rubberwhich slurry was applied on both sides of copper foil, and then driedand pressed to 0.22 mm thickness.

[0141] To fabricating batteries of AA battery size as shown in FIG. 11,a sheet of the positive electrode 35 and a sheet of the negativeelectrode 37 prepared above were wound while stacking between which aseparator 5 of polypropylene porous film was interposed, and placed in acan casing 71 with an electrolyte containing LiPF₆ in a mixture solvent.An inner bottom of the casing 71 was connected to the copper foil 63 touse for an outer negative terminal, and then an top opening of thecasing was sealed with a metal cover 61 for using a positive terminal 61which metal cover is connected to the electrode metal material 1 vialeads, thus obtaining lithium ion secondary batteries having nominalcapacity of 1800 mAh.

[0142] The batteries thus fabricated were tested to determine 2C and0.2C capacitance after repeating 50 charges to 4.3V and discharges by3.0V with a constant current of 100 mA in an incubator holding atemperature at 25° C. From these date, capacity retention of the testedbatteries are evaluated and the results are shown in Table 4. TABLE 3Capacity Retention (%) 0.2 C 2 C Example 12 90 58 Example 13 95 63Example 14 88 55 Example 15 94 61 Example 16 85 53 Example 17 92 60Comparative 4 48 12

[0143] In Comparative Example 4 in Table 3, conventional aluminum foilof four-nine grade having thickness of 20 μm, which had not embeddedwith carbon particles, was used as electrode metal material to support apositive electrode for the same battery.

[0144] It is seen from Table 2 that the batteries of these Examples12-17 are higher in capacity retention, particularly, exhibit moreexcellent high-rate performance as compared to the battery ofComparative Example 4. This shows that carbon particles embedded in andexposed to the surface of the electrode metal material can increaseconductivity between a positive electrode and a supporter using theelectrode metal material for a positive electrode. Event though oxidefilm are gradually produced on the metallic surface of the electrodeduring the cycle test of repeating charges and discharges, conductivitydue to carbon particles can be kept high to maintain high capacityretention of the battery. Also, passivation formed on a carbon embeddedelectrode metal material by anodizing is found to maintain stability ofthe high retention performance even after the cycling test.

[0145] The electrode metal material in accordance with the presentinvention is used to form a capacitor electrode structure making contactwith electrolyte, and includes numerous carbon particles on the surfaceof the valve metal material. Therefore, electric connection can beensured between a carbon electrode member, such as activated carbonparticles, to which the electrode metal material is joined, and theelectrolyte, whereby a stable electrode structure can be obtained. Forthis reason, the electrode function of this electrode metal material isnot deteriorated even if the material is used in the presence of waterin the electrolyte.

[0146] In addition, the carbon particles of the electrode metal materialcan be fixed in the surface of the valve metal material so as to beexposed to the surface, thereby enhancing electric connection andjoining to the electrode members.

[0147] Furthermore, when the surface of the valve metal material of theelectrode metal material is coated with a passive film, highconductivity to the electrode members and the electrolyte can be ensuredstably for extended periods of time. The electrode metal material inaccordance with the present invention is coated with an activated carbonlayer, and can be used as the double-layer electrodes of an electricdouble-layer capacitor. Therefore, it is possible to attain an electricdouble-layer capacitor having a low internal resistance and a largecapacitance value.

[0148] Moreover, the electrode metal material, making contact withelectrolyte, is used as the cathode of an electrolytic capacitor,whereby it is possible to obtain a cathode having stable conductivityfor extended periods of time. Therefore, it is possible to attain anelectrolytic capacitor having a low internal resistance and a largecapacitance value.

INDUSTRIAL USABILITY

[0149] The electrode metal materials in accordance with the presentinvention can be produced in the fields of the metal industry andelectronic component materials, and can be used as electrode materialsfor electric double-layer capacitors and electrolytic capacitors.Furthermore, the capacitors in accordance with the present invention canbe widely produced and used as electronic components in the field ofelectronic component materials, and can be applied to a wide range ofvarious electronic apparatuses.

1. An electrode metal material for using in an electrode structure incontact with non-aqueous electrolyte, wherein the electrode metalmaterial is a carbon-containing metal material comprising a valve metalmaterial and numerous carbon particles fixed in a surface of the valvemetal material and exposed to the surface thereof.
 2. The electrodemetal material according to claim 1, wherein said carbon particles areprojected from the surface of said valve metal material to expose tosaid surface.
 3. The electrode metal material according to claim 1,wherein the metallic surface of said carbon-containing metal material iscoated with a passive film.
 4. The electrode metal material according toclaim 1, wherein said electrode metal material is coated with anactivated carbon layer to form a double-layer electrode for an electricdouble-layer capacitor.
 5. The electrode metal material according toclaim 1, wherein said electrode metal material is a cathode of anelectrolytic capacitor, making contact with non-aqueous electrolyte. 6.The electrode metal material according to claim 1, wherein saidelectrode metal material is thin sheet.
 7. The electrode metal materialaccording claim 1, wherein said carbon particles are formed ofconductive carbon particles, such as graphite or carbon black.
 8. Theelectrode metal material according to claim 1, wherein said carbonparticles are activated carbon particles.
 9. The electrode metalmaterial according to claim 1, wherein said carbon particles have a meandiameter of the range of 0.01 to 50 μm.
 10. The electrode metal materialaccording to claim 1, wherein said carbon particles have one ofparticulate, granular and fibrous forms.
 11. A method of producing anelectrode metal material, being a carbon-containing metal materialcomprising a valve metal material and numerous carbon particles fixed inat least a surface of said valve metal material and exposed to saidsurface, wherein said method comprises the steps of: including saidcarbon particles in a valve metal ingot by heating and pressurizing amixture of valve metal powder and carbon powder in a container; and,forming said obtained valve metal ingot into a desired shape so as to beused as said carbon-containing metal material.
 12. A method of producingan electrode metal material, being a carbon-containing metal materialcomprising a valve metal material fixed numerous carbon particles in atleast a surface thereof, wherein said method comprises: dispersingcarbon particles on the surface of a valve metal material; and embeddingthe carbon particles into the surface of said valve metal material bypressurizing said carbon particles onto the surface of said valve metalmaterial to obtain said carbon-containing metal material.
 13. The methodof producing an electrode metal material according to claim 11, whereinsaid carbon embedding step uses a press method in which said carbonparticles are driven by using a die.
 14. The method of producing anelectrode metal material according to claim 11, wherein said carbonembedding step uses a rolling method in which said carbon particles aredriven by using a roller.
 15. The method of producing an electrode metalmaterial according to claim 11, wherein said carbon embedding step iscarried out when said valve metal material is formed by hot or coldworking.
 16. The method of producing an electrode metal materialaccording to claim 11, wherein the method comprises a step of coarseningthe surface of said carbon-containing metal material.
 17. The method ofproducing an electrode metal material according to claim 11 or 12,wherein the method further comprises a further step of exposing saidcarbon particles to the surface of said carbon-containing metal materialby etching said carbon-containing metal material in an acidic aqueoussolution.
 18. The method of producing an electrode metal materialaccording to claim 11 or 12, wherein the method comprises a step ofexposing said carbon particles to the surface of said carbon-containingmetal material by blasting said carbon-containing metal material. 19.The method of producing an electrode metal material according to claim17, wherein the method comprises a step of forming a passive film on themetallic surface of said carbon-containing metal material after saidstep of exposing said carbon particles.
 20. The method of producing anelectrode metal material according to claim 11 or 12, wherein saidcarbon particles are formed of conductive carbon particles, such asgraphite or carbon black.
 21. The method of producing an electrode metalmaterial according to claim 11 or 12, wherein said carbon particles areactivated carbon particles.
 22. The method of producing an electrodemetal material according to claim 11 or 12, wherein the diameter of saidcarbon particles is in the range of 0.01 to 50 μm.
 23. The method ofproducing an electrode metal material according to claim 11 or 12,wherein said carbon particles have one of particulate, granular andfibrous forms.
 24. A capacitor comprising a pair of electrodes andnon-aqueous electrolyte, wherein at least one electrode includes anelectrode metal material which is a carbon-containing metal materialcomprising a valve metal material and numerous carbon particles fixed inthe surface of said valve metal material and exposed to said surface.25. The capacitor according to claim 24, wherein said capacitor is anelectric double-layer capacitor, and said pair of electrodes is formedof electric double-layer electrodes each comprising saidcarbon-containing metal material and an activated carbon layer formed incontact with said carbon particles on the surface of said metalmaterial.
 26. The capacitor according to claim 25, wherein said valvemetal material is a flexible sheet, said pair of electric double-layerelectrodes is disposed face-to-face with a separator therebetween andwound, and enclosed in a container to obtain a winding type electricdouble-layer capacitor.
 27. The capacitor according to claim 25, whereinsaid activated carbon layers of said pair of electric double-layerelectrodes are accommodated in a container with a separatortherebetween, and said valve metal materials of said electrodes areaccommodated in the metallic lid and bottom portions of a container,which are coupled so as to be insulated from each other.
 28. Thecapacitor according to claim 27, wherein said metallic lid and bottomportions of said container are clad with said valve metal materials. 29.The capacitor according to claim 24, wherein said capacitor is anelectrolytic capacitor, one of said electrode metal materials is used asthe cathode, and the other electrode metal material having a dielectricinsulating film is used as the anode.
 30. The capacitor according toclaim 24, wherein said carbon particles are formed of conductive carbonparticles, such as graphite or carbon black.
 31. The capacitor accordingto claim 24, wherein said carbon particles are activated carbonparticles.
 32. The capacitor according to claim 24, wherein the diameterof said carbon particles is in the range of 0.01 to 50 μm.
 33. Thecapacitor according to claim 24, wherein said carbon particles have oneof particulate, granular and fibrous forms.
 34. The capacitor accordingto claim 24, wherein a passive film is formed on the metallic surface ofsaid valve metal material.
 35. A method of producing an electricdouble-layer capacitor comprising a pair of electric double-layerelectrodes each formed of an activated carbon layer formed on thesurface of a valve metal material, a separator for separating said pairof electric double-layer electrodes and non-aqueous electrolyte, whereinsaid method comprises the steps of: forming a carbon-containing metalmaterial in which numerous carbon particles are fixed in at least a thesurface of a valve metal material and exposed to said surface; applyinga paste containing activated carbon particles to the surface of saidcarbon-containing metal material; and drying and curing said paste toobtain said electric double-layer electrodes.
 36. The method ofproducing a capacitor according to claim 35, wherein, after the step offorming said carbon-containing metal material, said method furthercomprises a step of exposing said carbon particles on the surface ofsaid metal material by electrolytic etching said metal material in anacidic aqueous solution.
 37. A method of producing a button-typeelectric double-layer capacitor in which a pair of electric double-layerelectrodes, each having an activated carbon layer formed on the surfaceof an electrode metal material, is accommodated in a container with theactivated carbon layers laminated via a separator therebetween, and theelectrode metal materials are coupled to the metallic lid and bottomportions of the container, both portions being insulated from eachother, wherein said method comprises the steps of; forming acarbon-containing metal material, as the electrode metal material, inwhich numerous carbon particles are included at least in the surface ofa valve metal material and exposed to said surface; and applying theactivated carbon layers to the surfaces of the valve metal materials toobtain the electric double-layer electrodes.
 38. The method of producingan electric double-layer capacitor according to claim 37, including astep of previously carrying out cladding of the metallic bottom portionof said container with said valve metal materials at so as to accomplishintegration.
 39. A method of producing an electrolytic capacitor inwhich an anode formed of a valve metal material having a dielectricinsulating film on the surface thereof and a cathode formed of a valvemetal material are disposed face-to-face in non-aqueous electrolyte,wherein said method comprises a steps of forming a carbon-containingmetal material in which numerous carbon particles are fixed in at leasta surface of the valve metal material and exposed to said surface sothat the carbon-containing metal material is used as the electrode metalmaterial for the cathode.
 40. The method of producing a capacitoraccording to claim 35, 37 or 39, wherein the step of forming thecarbon-containing metal material includes a carbon embedding step ofdriving the carbon particles into the surface of the valve metalmaterial by pressurizing the carbon particles dispersed on the surfaceof said valve metal material to obtain the carbon-containing metalmaterial.
 41. The method of producing a capacitor according to claim 40,wherein said carbon embedding step uses a press method in which saidcarbon particles are driven by using a die.
 42. The method of producinga capacitor according to claim 40, wherein said carbon embedding stepuses a rolling method in which the carbon particles are driven by usingrollers.
 43. The method of producing a capacitor according to claim 41,wherein said carbon embedding step is carried out in a hot or coldworking step to form the valve metal material.
 44. The method ofproducing an electrode metal material according to claim 40, including astep of coarsening the surface of said carbon-containing metal material.45. The method of producing an electrode metal material according toclaim 40, wherein the method further includes a step of exposing saidcarbon particles to the surface of the carbon-containing metal materialby electrolytically etching the surface of the carbon-containing metalmaterial in an acidic aqueous solution.
 46. The method of producing anelectrode metal material according to claim 40, wherein the methodfurther includes a step of exposing said carbon particles to the surfaceof the carbon-containing metal material by blasting thecarbon-containing metal material.
 47. The method of producing anelectrode metal material according to claim 45, wherein the methodfurther includes a step of forming a passive film on the metallicsurface of the carbon-containing metal material after said carbonparticle exposing step.
 48. The method of producing an electrode metalmaterial according to claim 41, wherein said carbon particles are formedof conductive carbon particles, such as graphite or carbon black. 49.The method of producing a capacitor according to claim 42, wherein saidcarbon embedding step is carried out in a hot or cold working step toform the valve metal material.
 50. The method of producing an electrodemetal material according to claim 42, wherein the method furtherincludes a step of exposing said carbon particles to the surface of thecarbon-containing metal material by blasting the carbon-containing metalmaterial.
 51. The method of producing an electrode metal materialaccording to claim 43, wherein the method further includes a step ofexposing said carbon particles to the surface of the carbon-containingmetal material by blasting the carbon-containing metal material.
 52. Themethod of producing an electrode metal material according to claim 42,wherein said carbon particles are formed of conductive carbon particles,such as graphite or carbon black.
 53. The method of producing anelectrode metal material according to claim 43, wherein said carbonparticles are formed of conductive carbon particles, such as graphite orcarbon black.
 54. A non-aqueous secondary battery comprising a positiveelectrode and a negative electrode and non-aqueous electrolyte to makecontact to both the electrodes therein, wherein the positive electrodeis formed on an electrode metal material which is a carbon-containingmetal material comprising a valve metal material and numerous carbonparticles fixed in and exposed to a surface of the valve metal material.55. The non-aqueous secondary battery according to claim 54, wherein theelectrode metal material is a clad material comprising thecarbon-containing metal material and a base metal plate.
 56. Thenon-aqueous secondary battery according to claim 54, wherein a passivefilm thicker than a film to be naturally oxidized is formed on themetallic surface of the valve metal material.
 57. The non-aqueoussecondary battery according to claim 56, wherein the passive film hashigher withstand voltage than 3V.
 58. The non-aqueous secondary batteryaccording to claim 54, wherein the base metal is nickel or stainlesssteel.
 59. A method for producing a non-aqueous secondary batterycomprising: a positive electrode; a negative electrode; and non-aqueouselectrolyte to make contact with both the electrodes therein, whereinthe method comprises: forming a carbon containing electrode metalmaterial by embedding carbon particles into the surface of a sheet ofvalve metal material, the carbon particles exposing on the surface ofthe sheet; and applying a paste containing positive active substance onthe carbon containing electrode metal material for producing thepositive electrode.
 60. The method according to claim 59, wherein themethod further includes cladding the carbon containing electrode metalmaterial on a base metal plate in order to embed the carbon particles onthe surface of the sheet.
 61. The method according to claim 59, whereinthe method further includes previously cladding a sheet of the valvemetal material on a base metal plate to produce a clad which is embeddedwith the carbon particles.
 62. The method according to claim 60, whereinthe method further includes form a passive film on the surface of thecarbon containing electrode metal material.
 63. The method according toclaim 63, wherein the passive film is formed by anodizing the carboncontaining electrode metal material.
 64. The method of an electrodemetal material according to claim 13, wherein in the step of dispersingcarbon particles, a slurry containing the carbon particles is applied tothe surface.
 65. The method according to claim 64, wherein the slurrycontaining the carbon particles and solvent, without containing abinder.
 66. The method according to claim 64, wherein the methodincludes drying the slurry after applying on the valve metal material.67. The method according to claim 64, wherein the valve metal materialis roughened on the surface.
 68. The method according to claim 67,wherein the roughening of the valve metal material is performed byelectrolytically etching.
 69. The method according to claim 67, whereinthe roughening of the valve metal material is performed by chemicallyetching.
 70. The method according to claim 67, wherein the roughening ofthe valve metal material is performed by blasting technique.
 71. Themethod according to claim 64, wherein said carbon embedding step uses apress method in which said carbon particles are driven by using a die.72. The method of producing an electrode metal material according toclaim 64, wherein said carbon embedding step uses a rolling method inwhich said carbon particles are driven by using a roller.
 73. The methodof producing an electrode metal material according to claim 72, whereinthe roller is an roller embossed on its surface.
 74. The method ofproducing an electrode metal material according to claim 64, wherein themethod comprises a step of coarsening the surface of saidcarbon-containing metal material.
 75. The method of producing anelectrode metal material according to claim 64, wherein the methodfurther comprises a further step of exposing said carbon particles tothe surface of said carbon-containing metal material by etching saidcarbon-containing metal material in an acidic aqueous solution.
 76. Themethod of producing an electrode metal material according to claim 64,wherein the method comprises a step of exposing said carbon particles tothe surface of said carbon-containing metal material by blasting saidcarbon-containing metal material.
 77. The method of producing anelectrode metal material according to claim 75, wherein the methodcomprises a step of forming a passive film on the metallic surface ofsaid carbon-containing metal material after said step of exposing saidcarbon particles.
 78. The method of producing an electrode metalmaterial according to claim 77, the step of forming a passive filmincludes heat treating of the carbon-containing electrode material inair.
 79. The method of producing an electrode metal material accordingto claim 78, the heat treating is performed at 300°-620° C.
 80. Themethod of producing an electric double-layer capacitor according toclaim 35, wherein in the step of forming the carbon-containing metalmaterial, a slurry containing the carbon particles is applied to thesurface of the valve metal material, dried and drive into the surface ofthe valve metal material by pressing.
 81. The method according to claim80, wherein the slurry containing the carbon particles and solvent,without containing a binder.
 82. The method according to claim 80,wherein the method includes drying the slurry after applying on thevalve metal material.
 83. The method according to claim 80, wherein thevalve metal material is roughened on the surface.
 84. The methodaccording to claim 83, wherein the roughening of the valve metalmaterial is performed by electrolytically etching.
 85. The methodaccording to claim 83, wherein the roughening of the valve metalmaterial is performed by chemically etching.
 86. The method according toclaim 83, wherein the roughening of the valve metal material isperformed by blasting.
 87. The method according to claim 80, whereinsaid carbon embedding step uses a press method in which said carbonparticles are driven by using a die.
 88. The method of producing anelectric double-layer capacitor according to claim 80, wherein saidcarbon embedding step uses a rolling method in which said carbonparticles are driven by using a roller.
 89. The method of producing anelectric double-layer capacitor according to claim 88, wherein theroller is an roller embossed on its surface.
 90. The method of producingan electric double-layer capacitor according to claim 80, wherein themethod comprises a step of coarsening the surface of saidcarbon-containing metal material.
 91. The method of producing anelectric double-layer capacitor according to claim 80, wherein themethod further comprises a further step of exposing said carbonparticles to the surface of said carbon-containing metal material byetching said carbon-containing metal material in an acidic aqueoussolution.
 92. The method of producing an electric double-layer capacitoraccording to claim 80, wherein the method comprises a step of exposingsaid carbon particles to the surface of said carbon-containing metalmaterial by blasting said carbon-containing metal material.
 93. Themethod of producing a capacitor according to claim 80, wherein, afterthe step of forming said carbon-containing metal material, said methodfurther comprises a step of exposing said carbon particles on thesurface of said metal material by electrolytic etching said metalmaterial in an acidic aqueous solution.
 94. A method of producing abutton-type electric double-layer capacitor according to claim 80,wherein in the step of forming the carbon-containing metal material, aslurry containing the carbon particles is applied to the surface of thevalve metal material, dried and embedded into the surface of the valvemetal material by pressing.
 95. The method of producing an electricdouble-layer capacitor according to claim 94, wherein the method furtherincluding a step of previously cladding of the metallic bottom portionof said container with said valve metal materials at so as to accomplishintegration.
 96. The method according to claim 94, wherein the slurrycontaining the carbon particles and solvent, without containing abinder.
 97. The method according to claim 94, wherein the methodincludes drying the slurry after applying on the valve metal material.98. The method according to claim 94, wherein the valve metal materialis roughened on the surface.
 99. The method according to claim 98,wherein the roughening of the valve metal material is performed byelectrolytically etching.
 100. The method according to claim 98, whereinthe roughening of the valve metal material is performed by chemicallyetching.
 101. The method according to claim 98, wherein the rougheningof the valve metal material is performed by blasting sand technique.102. The method according to claim 94, wherein said carbon embeddingstep uses a press method in which said carbon particles are driven byusing a die.
 103. The method of producing a button-type electricdouble-layer capacitor according to claim 94, wherein said carbonembedding step uses a rolling method in which said carbon particles aredriven by using a roller.
 104. The method according to claim 72, whereinthe roller is an roller embossed on its surface.
 105. The method ofproducing a button-type electric double-layer capacitor according toclaim 94, wherein the method comprises a step of coarsening the surfaceof said carbon-containing metal material.
 106. The method of producing abutton-type electric double-layer capacitor according to claim 94,wherein the method further comprises a further step of exposing saidcarbon particles to the surface of said carbon-containing metal materialby etching said carbon-containing metal material in an acidic aqueoussolution.
 107. The method of producing a button-type electricdouble-layer capacitor according to claim 94, wherein the methodcomprises a step of exposing said carbon particles to the surface ofsaid carbon-containing metal material by blasting said carbon-containingmetal material.
 108. A method of producing an electrolytic capacitoraccording to claim 39, wherein in the step of forming acarbon-containing metal material, a slurry containing the carbonparticles is applied to the surface of the valve metal material, driedand drive into the surface of the valve metal material by pressing. 109.The method according to claim 108, wherein the method includes dryingthe slurry after applying on the valve metal material.
 110. The methodaccording to claim 108, wherein the valve metal material is roughened onthe surface.
 111. The method according to claim 110, wherein theroughening of the valve metal material is performed by electrolyticallyetching.
 112. The method according to claim 110, wherein the rougheningof the valve metal material is performed by chemically etching.
 113. Themethod according to claim 110, wherein the roughening of the valve metalmaterial is performed by blasting sand technique.
 114. The methodaccording to claim 108, wherein said carbon embedding step uses a pressmethod in which said carbon particles are driven by using a die. 115.The method of producing an electrolytic capacitor according to claim108, wherein said carbon embedding step uses a rolling method in whichsaid carbon particles are driven by using a roller.
 116. The method ofproducing an electrolytic capacitor according to claim 112, wherein theroller is an roller embossed on its surface.
 117. The method ofproducing an electrolytic capacitor according to claim 108, wherein themethod comprises a step of coarsening the surface of saidcarbon-containing metal material.
 118. The method of producing anelectrolytic capacitor according to claim 108, wherein the methodfurther comprises a further step of exposing said carbon particles tothe surface of said carbon-containing metal material by etching saidcarbon-containing metal material in an acidic aqueous solution.
 119. Themethod of producing an electrolytic capacitor according to claim 108,wherein the method comprises a step of exposing said carbon particles tothe surface of said carbon-containing metal material by blasting saidcarbon-containing metal material.
 120. The method of producing anelectrolytic capacitor according to claim 118, wherein the methodcomprises a step of forming a passive film on the metallic surface ofsaid carbon-containing metal material after said step of exposing saidcarbon particles.